One important structural element in communication equipment or communication systems is a frequency translation device. A frequency translation device translates the frequency of some signal to another frequency as in a mixer or a sampler. If the network characteristics of a frequency translation device can be accurately measured, the communication equipment or communication system can be optimized. Until now, several methods for measuring the network characteristics of a frequency translation device have been proposed. These methods measure the network characteristics of a frequency translation device by using a vector network analyzer. Some methods require S21=S12 to be satisfied in the network characteristics of the frequency translation device, which is the device under test (see Unexamined Japanese Patent Publication No. 2002-57530 (pages 2-3, FIG. 1). Other methods require a special structure for the vector network analyzer (see Unexamined Japanese Patent Publication No. 2002-202, 331 (pages 3-4, FIG. 1, FIG. 2). The special structure is a structure for measuring in the state with different source and receiver frequencies.
In the past few years, balanced input/balanced output frequency translation devices have become widely used. The network characteristics of a balanced input/balanced output frequency translation device can be measured by connecting a balun. However, in this measurement method, the network characteristics of the balun are included in the network characteristics of the frequency translation device. In addition, this measurement method cannot perform measurements related to the in-phase signal component.
The present invention is to provide a method for measuring the network characteristics of all frequency translation devices by using an ordinary vector network analyzer. In addition, the present invention will provide a method for accurately measuring the network characteristics of a balanced input/balanced output frequency translation device.